1. Field of the Invention
The invention relates to an electrode assembly and a lithium secondary (rechargeable) battery having the same, and more particularly to, an electrode assembly having a super-capacitor for allowing high-rate charge/discharge operations and a lithium secondary battery having the same.
2. Description of Related Art
Recently, compact and lightweight electric/electronic devices such as cellular phones, laptop computers, and camcorders are being widely developed and produced. Such portable electric/electronic devices are typically provided with a battery pack so that they can be operated in any place where a separate power supply is not connected. The battery pack has at least one battery to drive the portable electric/electronic devices for a predetermined time period.
Now, rechargeable secondary batteries are usually adopted in consideration with cost efficiency. For example, rechargeable secondary batteries such as Ni—Cd, Ni—MH, Li, and Li-ion batteries are available in the art.
Particularly, the lithium secondary battery has a high energy density per unit weight and an operation voltage of 3.6V, which is triple that of a Ni—Cd battery or a Ni—MH battery, which are widely used as power supplies for portable electronic devices. Therefore, the lithium secondary battery is increasingly used in the art.
In the lithium secondary battery, lithium based oxide is used as a positive electrode activation material, while a carbon based material is used as a negative electrode activation material. Generally, the lithium secondary battery is classified into either a liquid electrolyte battery or a polymer electrolyte battery depending on the electrolyte used therein. A battery using the liquid electrolyte is referred to as a lithium ion battery, and a battery using the polymer electrolyte is referred to as a lithium polymer battery. In addition, the lithium secondary battery is fabricated in a variety of shapes such as cylindrical, rectangular, pouch types, and the like.
Typically, a lithium secondary battery includes an electrode assembly, a case storing the electrode assembly, and an electrolyte injected into inside of the case to allow lithium ions to travel. The electrode assembly is formed by winding: a positive electrode plate to which a positive electrode tap is attached, a negative electrode plate to which a negative electrode tap is attached, and a separator interposed between the positive and negative electrode plates to prevent a short circuit and allow only lithium ions to travel.
The lithium secondary battery may be formed as follows.
First, a positive electrode is coated with a positive electrode activation material, and a positive electrode tap is connected thereto, and a negative electrode plate is coated with a negative electrode activation material, and a negative electrode tap is connected thereto. The coated positive electrode, coated negative electrode, and a separator are stacked and then wound to provide an electrode assembly.
Subsequently, the electrode assembly is inserted into a case so that the electrode assembly will not separate. Then, an electrolyte is injected into the case and the case is sealed, thereby completing the lithium secondary battery
However, a conventional lithium secondary battery does not satisfy the requirements of high energy density and output density for high performance electronic devices such as Global System for Mobile Communication (GSM) phones and hybrid vehicles.
Such high performance electronic devices require excellent initial discharge properties, and conventional lithium secondary batteries cannot satisfy this requirement.